求助

RT 菜鸡太菜了，仍然调不对

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
int n;
int k;
int ans;
int a[100005];
int b[100005];
int dp[100005];
int last[100005];
int main(){
    memset(last,0x3f,sizeof(last));
    scanf("%d",&n);
    for (int i=1;i<=n;i++){
        int k;
        scanf("%d",&k);
        a[k]=i;
    }
    for (int i=1;i<=n;i++){
        int k;
        scanf("%d",&k);
        b[k]=a[k];
    }
    k=1;
    dp[1]=1;
    last[1]=b[1];
    for (int i=2;i<=n;i++){
        int x=lower_bound(last+1,last+k+1,b[i])-last-1;
        dp[i]=x+1;
        last[x+1]=min(last[x+1],b[i]);
        k=max(k,x+1);
    }
    for (int i=2;i<=n;i++){
        ans=max(ans,dp[i]);
    }
    printf("%d\n",ans);
    return 0;
}